Conventionally, in controlling an industrial machine, such as a belt conveyor, by means of a CNC (numerical control device), control of a servomotor is executed in accordance with a command program that gives commands of a target position and a moving speed. In such a case, however, during the operation of the servomotor, the speed is not always constant, and acceleration or deceleration is effected as required. Conventionally, therefore, the timing for the acceleration or deceleration is commanded in accordance with points of contact at acceleration or deceleration point or by an operator's button operation. In such a conventional system,. on receiving this command, the CNC carries out acceleration or deceleration to a moving speed that is previously set in parameters.
According to the conventional system, however, the acceleration-deceleration control is controlled after receiving external signals from the points of contact, buttons, etc., so that there has been a problem of time lag in starting the control. Besides, the hardware must be set up according to the purpose, causing the operating procedure of the conventional system to become cumbersome and lacking in general-purpose applicability.